Burn Patients, and other Patients subject to extensive recuperative periods, must remain in bed for extended periods of time. When such patients lie supinely on a conventional mattress, most of the load is born by protuberances of the posterior surface of the body such as the heels, the buttocks, the scapulae, and the occipital region of the head. The relatively small areas of soft tissue at these points are then subjected to high pressures by being compressed between the skeleton and the supporting surface. When this pressure becomes great enough to cause collapse of small capillaries and veins, pressure sores or decubitus ulcers may result. Burn patients also have problems with rubbing against the surface of an immobile conventional mattress surface which can result in the extraction of a skin graft. In order to overcome these problems, hospital beds have been developed which use fluidized granular material (preferably spherical beads) as a supporting medium in order to uniformly distribute the supporting pressure points along the body surface, thus reducing the pressure at the aforementioned critical areas.
Fluidized bead beds comprise a tank partially filled with a mass of some granular material, the granular material resting on top of a diffuser board. A flexible, loose fitting sheet, which is permeable to air but not the granular material, is laid on top of the granular material to form the patient support surface. A gas, commonly air, is blown through the diffuser board into the granular material fluidizing the material so that a patient laying on top of the covering sheet is buoyantly susPended upon the bed. In this way, the forces imparted to the body are evenly distributed over the body and the chance of decubitus ulcers occurring is greatly lowered. Burn patients lie more comfortably, and the fluidized support medium moves with the body which reduces the likelihood of skin graft extraction. Also, this structure allows body fluids exuded from wounds to flow through the covering and into the granular material away from the patient, quickening the healing process. When the granular material is not being fluidized, the material settles down into a solid structure and contours to the body.
Although fluidized bead beds are quite satisfactory in accomplishing the objectives enumerated above, they are not without some disadvantages. When bead beds are operated for an extended period of time, heating of the room air becomes a problem. This is because the air used to fluidize the beads must be pressurized by a compressor or other type of blower. The air is necessarily heated as the compressor does work on it, and when the air is exhausted through the cover sheet, the ambient temperature of the room is raised. Another disadvantage comes about when it is desired to transfer a transfer the patient off of the bed because the level of the granular material supporting the patient is below the rim of the tank. The situation is worsened if the bed is fluidized since the patient sinks even further down. Another difficult arises when it is desired to roll the patient on his side in order to perform various clinical procedures. The location of the surface within the tank structure below the level of the rim makes it difficult for hospital personnel to manually roll the patient over onto his side. The procedure is rendered even more difficult in the case of burn patients who are sensitive to manual manipulation.
Therefore, it is an object of the present invention to provide a fluidized bead bed capable of operating without exhausting heated air into the room.
It is a further object to provide a fluidized bead bed with a means for positioning a patient on his side with no need for manual manipulation of the patient by hospital personnel.
It is a still further object to provide a fluidized bead bed with a means for facilitating the transfer of the patient off of the bed.